Method and apparatus for spinning uniform fibers



April 1969 A. o. MOGENSEN ETAL 3,436,448

METHOD AND APPARATUS FOR SPINNING UNIFORM FIBERS Filed Feb. 5. 1966 INVENTORS. GE NS E N United States Patent U.S. Cl. 264-176 7 Claims ABSTRACT OF THE DISCLOSURE Method and apparatus for swirling a fiber-forming liquid polymer mass immediately prior to extruding such mass through a plurality of orifices in a single spinnerette in order to reduce thermal gradients and/or concentration gradients to minimize variations in size of fibers formed from the various orifices of the spinnerette. Two specific devices are disclosed.

Thi invention relates to processes and apparatus for simultaneously spinning a plurality of fibers from each spinnerette. More particularly, this invention relates to an improvement in such processes and apparatus which improves the uniformity of the fiber so spun by swirling the material to be extruded immediately prior to its passage through the spinnerette orifices.

Various processes are known for the spinning of synthetic fibers, such as melt spinning, dry spinning, and wet spinning. In melt spinning, molten polymer is extruded into a cold coagulating medium to solidify the fibers by cooling. In dry spinning, a solution of polymer in a volatile solvent is extruded into a heated gaseous coagulating medium to solidify the fibers by evaporation of solvent. In wet spinning, a polymer solution is extruded into a coagulating medium which solidifies the fibers by chemical reaction and/or leaching of solvent from the polymer solution. In each of these processes, a fiberforming liquid polymer mass, which may be a polymer melt such as in the spinning of nylon or glass, or a polymer solution, such as in the spinning of rayon or acrylics is first produced. This fiber-forming liquid polymer mass is then extruded into a suitable coagulating medium where it is solidified in fiber form.

To be useful for the spinning of fibers, the fiber-forming liquid polymer mass is normally of relatively high viscosity. Normally, it flows through the fluid passageway within the spinnerette holder at a velocity sufficiently low that the liquid flows in laminar flow without substantial mixing. Thus, any inhomogeneities present in this viscous liquid within the spinnerette holder will serve to present to the various orifices in the spinnerette liquid having different fiber forming properties. Illustrative of the variations possible in the fiber-forming liquid polymer mass are (a) differences in concentration of polymer in polymer solutions used in wet spinning or dry spinning and (b) dilferences in viscosity caused by dilferences in temperature where the fiber-forming liquid polymer mass at one temperature is extruded into a coagulating medium at a different temperature as in the case of melt spinning, dry spinning, and many wet spinning processes.

When spinning a plurality of fibers from a single spinnerette having a plurality of orifices of identical size and shape, the rate of flow through the various orifices i a function of the viscosity of the fiber-forming liquid polymer mass. To the extent that the viscosity differs from orifice to orifice (due to thermal gradients and/or concentration gradients) the flows through the various orifices will differ, producing fibers of differing sizes. To the extent that the polymer solutions going through the various orifices are of differing concentrations, the fibers formed therefrom after coagulation will be of differing sizes even where the polymer solution flow rates can be maintained equal. Not only are these variations undesirable of themselves since they are uncontrolled, but such variations may lead to spinning difficulties causing individual fibers to break at the spinnerette while the remainder of the fiber bundle continues to spin.

It is a prime object of this invention to provide for the elimination of this difiiculty with the attendant adverse effects. Thus, it is an object of the present invention to eliminate the spinning difiiculties which produce defects of the types above described which are caused by lack of homogeneity of the fiber-forming liquid polymer mass reaching the spinnerette orifices. It is a further object of this invention to accomplish this purpose in a simple, efficient, effective manner without introducing undue complications into the spinning process.

These objects, and other objects a will appear hereinafter are mainly achieved by swirling the fiber-forming liquid polymer mass within the spinnerette holder immediately prior to passage through the spinnerette orifices. Preferably this is accomplished by positioning within the passageway adjacent or within the spinnerette a means for swirling the fiber-forming liquid polymer mass.

In one embodiment of the present invention such means will comprise a disc disposed parallel to and spaced from the spinnerette, which disc is provided with a plurality of openings therethrough which are inclined tangentially. This disc may be supported by a generally cylindrical insert which may serve as insulation between the fiber-forming liquid polymer mass prior to extrusion and the environment external to the spinnerette.

In another embodiment, such means may comprise a helical coil surrounding a solid cylinder whose axis is substantially perpendicular to the spinnerette.

For a clearer and more detailed description of the present invention as embodied in specific embodiments thereof, reference may be had to the following description taken in conjunction with the accompanying drawings wherein:

FIGURE 1 is a cross section of a fiber-forming spinnerette provided with an insert in accordance with one embodiment of the present invention;

FIGURE 2 is a plan view of the disc 20 of FIGURE 1; and

FIGURE 3 is a cross sectional view, similar to FIG- URE l, but of a second embodiment of the present invention.

Referring to the drawings, and more particularly to FIGURES 1 and 2, there is shown a typical fiber-forming spinnerette 11 provided with a plurality of orifices 12 which is mounted in the usual manner in a spinnerette holder 13. Specific details of these elements will not be given since these are conventional in the art of spinning synthetic fibers.

In accordance with the principles of the present invention, there is positioned within the spinnerette 11 a disc 20 which serves to swirl the fiber-forming liquid polymer mass within spinnerette 11 immediately prior to extrusion through orifices 12. In order to space disc 20 the required distance from the face of spinnerette 11 to avoid blocking orifices 12, disc 20 is provided with a plug 21 which, when disc 20 is properly positioned, bears against a portion of spinnerette 11 which is free of orifices. In order to provide a swirling motion to the fluid passing through disc 20 it is provided with a plurality of openings 22 which are inclined tangentially, which means that they are inclined relative to the axis of the disc and the direction of flow of fluid and the inclination is tangential or substantially tangential rather than radial, substantially as shown in FIGURES l and 2.

Disc is supported in position within spinnerette 11 by a generally cylindrical insert 26 which also may serve to insulate the fiber-forming liquid polymer mass passing through the center thereof from the environment external to spinnerette 11.

It has been found desirable to incline openings 22 at an angle of about degrees to the axis of disc 20 and the direction of flow of fiuid to orifices 12 in spinnerette 11 in order to improve the mixing of the fluid immediately prior to extrusion.

Referring next to FIGURE 3, there is shown a second embodiment of the present invention which differs from the showing in FIGURE 1 in the provision of a different means for imparting the swirling motion to the fiberforming liquid polymer mass immediately prior to extrusion.

In this embodiment, the means for imparting a swirling motion to the fluid immediately prior to extrusion comprises a solid cylinder 31 surrounded by a helical coil 32 located within the spinnerette. This provides a helical passageway for the fluid external to the solid cylinder 31 between the coils of helical coil 32. Preferably, end 33 of helical coil 32 is restrained within slot 34 in solid cylinder 31 to keep the opposite end of coil 32 from obstructing the orifice in the spinnerette.

As is obvious, all parts should be made of materials which are inert in the environment in which they are to be used. Thus, the spinnerette 11 must be stable to chemical attack both from the fiber-forming liquid polymer mass and the coagulating medium and must not be adversely affected at the temperatures used in spinning fibers. These considerations are well known in the fiber spinning art and spinnerette 11 may be made of any material conventional for the purpose. Similarly, the means for swirling the fluid must be inert to chemical attack and thermal degradation by the fiber-forming liquid polymer mass. Thus, such means may be made of the same material as the spinnerette. Alternatively, since the means for swirling the fiber-forming liquid polymer mass does not have any critical dimension as required for spinnerette orifices, it may be made of materials which would not quite be suitable for spinnerettes. Illustrative of such materials are plastics, such as nylon, Teflon, etc. In the embodiment of FIGURE 1, when using a fiber-forming liquid polymer mass at a temperature substantially different from the temperature of the coagulating environment, it may be desirable to make insert 26 of a material possessing thermal insulating properties.

It is also considered desirable that the means for swirling the fluid occupy at least half of the volume within the spinnerette in order to reduce the time available for the coagulating environment to change the temperature of the fluid within the spinnerette and to provide for a higher velocity of fluid flow within the spinnerette to better homogenize such fluid.

The following example illustrates the improvements obtained in the uniformity of fibers produced when using the principles of the present invention as compared with conventional spinning.

A 75 denier, 35 filament acrylic fiber thread was spun from a concentrated aqueous sodium thiocyanate solution of a copolymer of acrylonitrile with methyl methacrylate using a spinnerette assembly substantially as shown in FIGURE 1. Using ASTM Standard Tested Method for Textile Material, D 1577-63T, the denier was determined for each of 20 filaments from each spinning positions total production of 35 filaments.

Four identical positions on a spinning machine were used. On two positions, fibers were spun using a spinnerette assembly substantially as shown in FIGURE 1 while on the other two positions the means for swirling the fluid to be extruded was omitted. Two doffs were collected and then the positions were interchanged and two more dotfs were collected. This served to eliminate any uncontrollable or unknown variations among the four positions. In the subjoined table, data is presented for the four dotfs of each of the four positions in terms of the range of deniers per filament (maximum denier per filament-minimum denier per filament among the 20 tested of the 35 in the yarn) and the coefficient of variation (percent C.V.= 100x the standard deviation/mean denier per filament).

TABLE Position 1 2 3 4 Swirling means Yes N 0 Yes No Range of d./f.:

RunNo.1 .43 .75 .67 .90

RunNo.2 .45 .80 .55 .80 Percent C.V. of d./i.

Run No.1 5. 5 8.6 7 9 10.5

Run No.2 5.6 8. 9 7 0 11. 1

Position 1 2 3 4 Swirling means No Yes No Yes Range d./f.

Run No. 3 48 .62 57 Run No. 4 93 .45 1. l0 57 Percent CV. of d./l'.

Run No.3 11.5 5. 6 8. 5 7.1

Run No. 4- 12.2 7.0 13.9 6.3

From this table it is readily apparent that a substantial improvement in the uniformity of fibers produced was achieved when using a means for swirling the fluid immediately prior to extrusion when compared to the otherwise identical spinning without such means.

We claim:

1. In the process of simultaneously spinning a plurality of fibers from a single spinnerette which includes preparing a fiber-forming liquid polymer mass and extruding said mass through a plurality of orifices in a single spinnerette into a coagulating medium, the improvement comprising swirling said mass immediately prior to the extrusion thereof.

2. A process as defined in claim 1 wherein said fiberforming liquid polymer mass prior to extrusion is at a temperature different than said coagulating medium.

3. A spinnerette assembly comprising, in combination, a spinnerette having a plurality of orifices disposed therein; mounting means for supporting said spinnerette provided with a fluid passageway therein communicating with said orifices; and means within said passageway adjacent said spinnerette for swirling fluid flowing through said passageway immediately prior to passage of said fluid through said orifices.

4. A spinnerette assembly as defined in claim 3 wherein said means for swirling fluid comprises a disc disposed parallel to and spaced from said spinnerette, said disc being provided with a plurality of openings therethrough, each of said openings being inclined tangentially to impart a swirling motion to fluid passing therethrough.

5. A spinnerette assembly as defined in claim 4 including support means for supporting said disc comprising a generally cylindrical insert into which said disc is fitted, said insert serving also as insulation between said fluid and the environment exterior to said spinnerette.

6'. A spinnerette assembly as defined in claim 3 wherein said means for swirling fluid comprises means defining a helical passageway, the axis of which is substantially perpendicular to said spinnerette.

7. A spinnerette assembly as defined in claim 6 wherein said means defining a helical passageway comprises a helical coil surrounding a solid cylinder.

References Cited UNITED STATES PATENTS 2,469,999 5/1949 Stofer.

(Other references on following page) UNITED STATES PATENTS FOREIGN PATENTS Braunlich. 885,358 12/ 1961 Great Britain. Reding 264349 970,285 9/ 1964 Great Britain. Hill. 643,669 1937 Germany.

JULIUS FROME, Primary Examiner. Barlow et al. J. H. WOO, Assistant Examiner. Davis.

1 1 US. Cl. X.R. Snella et a1 264176 X 10 Heijnis. 

